1. The Microscope

2. Compound Microscope Uses multiple lenses to:
Collect light from the sample
Then a separate set of lenses to focus the light into the eye or camera
Heavier, larger, and more expensive than simple microscopes due to the increased number of lenses used in construction

3. Compound Microscope

4. Advantage of Multiple Lenses
Improved Numerical Aperture
Reduced Chromatic Aberration
Exchangeable objective lenses to adjust the magnification
Has the ability to change the amount of light that is on the specimen

5. Improved Numerical Aperture
Consenser: an opening through which light travels
You can change the width of the condenser
More narrow: the light rays are more collected
Sharp focus onto the image plan
More wide: rays are more dispersed
Focus is sharp around what the lens is focusing on and blurred towards the perimeter

6. Reduced Chromatic Aberration
Chromatic aberration distortion in which there is a failure of a lens to focus all colors
This occurs because the lenses have a different refractive index for different wavelengths of light
Refractive index – bending of light

7. Has the ability to change the amount of light that is on the specimen
Iris Diaphragm: allows the different refractive indexes of the specimen to be observed
Regulates the amount of light that passes through the condenser

8. Limitation of Multiple Lenses
Cannot distinguish between objects that are less than 0.2 μm apart – the images are seen fused together
This is called the Resolution

10. Condenser
Iris Diaphragm

11. Resolution
The ability to discriminate between two close objects as separate

12. Resolving power is determined by the amount and physical properties of the visible light that enters the microscope
The more light that enters the objective lens, the greater the resolution
The size of the aperture (opening) of the lens decreases with increasing magnification, allowing less light to enter the objective
So you will need to increase the light intensity at the higher magnifications

13. How to properly carry a microscope
Upright
One hand on its arm
One hand supporting its base
Avoid swinging and jarring when setting it down

14. How to Clean the Lens Special grit-free lens paper
Use circular motion to wipe the lens
Clean ALL lenses before and after use

15. Always begin focusing with the lowest-power objective (10x) objective lens in position, changing to the higher power as necessary.

16. Wet Mounts
Used to look at cells and tissues
Mix the cells with physiologic saline
Can stain with methylene blue
Always use a coverslip with temporary (wet mount) preparations.

17. Returning the microscope to the storage cabinet:
Remove the slide from the stage
Rotate the lowest-power objective lens into position
Wrap the cord neatly around the base
Replace the dust cover or return the microscope to the appropriate storage area

18. Never remove any parts from the microscope; inform your instructor of any mechanical problems that arise.

19. Magnification Two lenses that magnify: Ocular Objective:
Magnifies the specimen to produce a real image
The real image is projected to the ocular
The real image is then magnified even further by the ocular to produce the virtual image

20. Total Magnification
Total Magnification = Objective lens power * Ocular lens power
So if:
Ocular = 10x
Objective = 45x
Total Magnification =

21. Total Magnification
Total Magnification = Objective lens power * Ocular lens power
So if:
Ocular = 10x
Objective = 45x
Total Magnification = 10 * 45 = 450

22. Diameter of a Microscopic Field
As you increase magnification, the field decreases
Knowing the field size can tell you the size of your specimen

23. You can determine the size of the field:
Diameter field A * Total magnification field A = Diameter field B * Total magnification fieldB
Diameter field B = (diameter field A * Total magnification field A)/Total mag Field B